Power-limiting amplifying device



Aug. 12, 1924. 1,504,537

H. DE F. ARNOLD POWER LIMITING AMPLIFYING DEVICE Original File d Sept. 5, 1915 Patented Aug. 12, 1924.

UNITED STATES PATENT orries.

HAROLD DE FOREST ARNOLD, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORA- TION OF NEW YORK.

POWER-LIIVIITING AMPLIFYING DEVICE.

Application filed September 3, 1915, Serial No. 48,873, Renewed September 14, 1922. Serial No. 588,285.

To all 'whom it may concern Be it known that I, HAROLD DE FOREST ARNOLD, a citizen of the United States, residing at Maplewood, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Power- Limiting Amplifying Devices, of which the following is a full, clear, concise, and exact description.

This invention relates to power limiting repeating and amplifying devices, and especially to devices of this kind which are adapted to be used in radio communication systems for limiting the electrical power which may be transmitted to a receiving instrument in such a system, and more particularly to devices in which such limiting action is obtained by utilizing the properties of thermionic or equivalent discharge de vices.

An object is to provide rapidly responsive means by which a definite upper limit is set upon the amount of power which may be communicated to a receiving circuit or apparatus, while amounts of power below said limit may be transmitted without interference.

The ability to secure such limitation is desirable, in a radio receiving system for example, because foreign disturbances, which in the wireless are often of large magnitude compared with that of the received signals, may be reduced to a value not exceeding that of the signals, thus securing hlgher intelligibility in reception.

In a general aspect, the objectof this invention is to provide improved circuits and means for association with thermionic repeating devices. The objects of the invention may be accomplished by the apparatus herein disclosed wherein, unilaterally conducting elements, placed in opposition in a circuit, limit the current which may flow in either direction around that circuit, and in this respect this invention is similar to that which forms the subject of my Patent N o.

1,168,270 for a protection device for electric circuits, granted January 18, 1916. It

dilfers from that, however, in that additional elements are associated with the 111111 lateral devices, and elsewhere, to secure certain improvements in operation, as explained later in this specification, and also in that an amplifying-effect is obtained which makes this device particularly applicable in radio communication.

In the preferred form of this device the part of the circuit to lie in the paths of thermionic currents between hotcathodes and cold anodes, said thermionic currents being oppositely directed with respect to said circuit. These thermionic currents are caused to flow by impressing upon their limiting electrodes, in multiple, an electromotive force operating through a high impedance, said high impedance performing an important function in connection with the power or current limiting action of the device as hereinafter described. This high impedance serves to differentiate this power limiting device from the repeating device described in U. S. Patent No. 1,128,292, to E. H. Colpitts for an electric wave amplifier, as will be apparent from the further explanation of its function given later.

The nature of this invention will be more fully understood by reference-to the draw ing, which represents a receiving system for radio communication embodying this invention, and in which '1 represents an elevated receiving conductor, 2 a tuning inductance coil, 3 an adjustable condenser, and 4: an adjustable resistance shunting the condenser. By means of the coil 5, the tuned circuit 5, 6 is coupled to the antenna. The terminals of the condenser 6 are connected to the input circuit of the thermionic repeater 7, comprising heated filamentS. grid 9 and-plate 10. A battery 11. is preferably connected in the input circuit to maintain the grid at a negative potential with respect to the filament. 12 is a battery which serves to heat the filament 8. The output circuit of repeater 7 contains battery 15 and a choke coil 16, shunted by a condenser 14: to

afford a path for high frequency power, and the coils 13' and 17, the latter having reversible inductive connection with coil 5-,

' the sense of its inductive action being controlled by reversing switch 18. The purpose of coil 17 is to neutralize the coupling unilateral conductivity is secured by causing between input and output circuits of the amplifier 7 and thus prevent free oscillation or singing. The coil 19, coupled to 13, connects the above described amplifying circuit to the tuned circuit 19, 20. Across the terminals of condenser 20 is connected the input circuit of a detecting device which comprises thermipnic element 21, condenser 22 and resistance 23. The purpose of the combination of the condenser and high resistance in connection with thermionic element 21 is as follows: \Vhcn a positive charge, for example, is forced upon the grid of element 21, this charge neutralized by electrons from the filament. Then when, in the next alternation, a negative charge is forced to the grid by the incoming wave, this charge adds to that already present and produces a still larger negative charge upon the grid, since a negative charge cannot be neutralized by the electron stream. The condenser therefore aids in decreasing the average current in the output circuit. The grid must, however, be conductively connected to the incoming circuit, otherwise the accumulated negative charge would remain and prevent further operation. To provide for this, a high resistance leakage path is shunted around the condenser to allow a leak which is slow compared with the period of high frequency currents, but still rapid enough to permit considerable leakage in a time comparable with the period of telephonic waves. The output circuit of this thermionic element is supplied with current by batteries 15 and 27, acting through choke coil 28 and resistauce 25, condenser 24 serving as a high-frequency shunt, and condenser 26 to limit the direct current to the detector circuit. 31 is an amplifier having a battery 30 in series with its grid and a re sistance 29 across its input circuit. The output circuit of amplifier 31 comprises a battery 34 and choke coil 35, both shunted by condenser 33, and a coil 32. Coil 36, coupled with 32, supplies power to resistance 37, across a portion of which is connected the input circuit of another amplifier 38, having a battery 39 in its grid circuit. The out put circuit of amplifier 38 is supplied by battery 34 and contains choke coil 42, con denser 40 and coil 41, whose functions are the same as those of the corresponding elements in the previous amplifier. It also contains condenser 43 and coil 44. The apparatus to the right of 44'comprises the powerlimiting device and the receiving circuit.

In this device coil 45' is coupled to coil 44. 46 is a resistance. 48, 49 and 53 are the filament, grid and plate, respectively, of a structure of the audion type, as are also 50, 51, 52, respectively. 47 is a battery common to the input circuits of the two structures. which structures may be in the same vessel or in separate vessels. 54 is a transformer winding connecting plates 52 and 53 and having a connection :brought out at its middle point. The secondary winding 55 of this transformer leads to a receiving instrument 66, preferably through the con- '70 densers 59.

Current is supplied to the output circuits of the last mentioned structures of the audion type by battery (55 connected through coil 57, and the variable high resistance 58 76 to the middle point of coil 54 and to the common point of the two filaments 48 and 50. Condenser 56 and choke coil 57 tend to prevent fluctuations of current'from the source from passing through the thermionic elements and coils 54. set is grounded at the points and 64.

The operation of this system is as follows:

The receiving c0, c1, c2, 03

Power received by the antenna is transferred to the circuit 5, 6, augmented by am-' plifier 7, communicated to circuit 19, 20, transformed into low frequencyform by detection in element 21, augmented by amplifiers 31 and 38, and passed to the receiving instrument through the power limiting device whose operation will now be explained.

The thermionic repeater being unilaterally conducting, the repeater element 48, 49, 53

can transmit positive current due to battery 65, only in the direction from 53 to 48. Also, element 50, 51, 52 can transmit positive direct current only in the direction from 52 to 50. If these currents are approximately equal, it follows that the maximum variation in current around the circuit 48, 53, 54, 52, 50 can never exceed the magnitude of the normal current in either element, provided none of this varied current can pass through that part of the circuit of the battery 65 which is common to the two thermionic elements. To prevent any appreciable passage of variable current the high 1 tage is ternating or varying current in windin 55 larger than the normal space current 0 the elements. This normal space current is adjusted until its value is just greater than the amplitude of the signals to be received.

The resistance 58 prevents serious unbalance of currents in the two halves of winding 54, when a large electromotive force is impressed, by lowering the effective potential difference between plate and filament by the amount of the voltage drop in the 1 said resistance, and conequently decreasing the current which can flow in the out ut circuit of either repeater element, this e ect being a fundamental one in the operation of the thermionic repeater.

Owing to the fact that the vacuum tube repeaters can transmit current in one direct1on only, 1t 15 impossible to do more by any impulse than to decrease the current in one vacuum tube repeater tov zero." The current in. the other tends to increase in accordance with the increase of potential on the grid.

The total'drop of potential in the output circuit is made up of two parts, that across the tube between the anode and cathode and that across the resistance 58. I

If now the current is increased, not by increasing the electromotive force of the battery or source 65, but by increasing the potential difference between the cathode and the grid, the current through the resistance 58 increases. Since the output source 65 remains constant, it follows that the drop of potential across the tube decreases while that across the resistances 58 increases A choking effect is thus produced by the resistance 58 with the result that, as the grid potential becomes greater, more and more current is diverted to the grid. A point is finally reached where no measurable increase in anode-cathode current is produced by increasing the grid potential. If the maximum amount of current is made approximately equal to the current required to transmit the talk, the interfering sounds, due to accidental causes, cannot possibly be of greater intensity than the speech.

What is claimed is:

1. A receiving system for radio communication comprising an antenna, a tuned receiving circuit connected therewith, means for amplifying the power of waves communicated to said tuned circuit. means fortected waves, and means including thervmionic-elements for limiting the power transmittedby said waves to said translating device.

2. In combination w1th a source of power,

a power limiting device comprising electric.

discharge devices each including an impedance controlling element, said devices having divided input and divided output circuits, a connection of said input circuit to said source of power, a high impedance path containing a source of electromotive force and connected between the points of d1v1s1on of said divided circuits, a receiving device and transformer windings for connecting sald output circuit to said receiving device.

3. A receiving system for radio communi-- cation comprising an antenna, a receiving circult connected therewith, means for amto sa-id detected waves, and a power limiting device comprising a thermionic repeater with dividedinput and divided output cir-' cuits, a highimpedance path containing a .source of electromotive force connected in the output circuit of said repeater and transformer windings for connecting said output circuit to said translating means.

4. Ina powerlimiting device, the combination of a plurality of evacuated vessels each including a unilaterally conductive space, an impedance controlling element for said space, said spaces being connected in opposition-in a circuit, a hlgh impedance path and a source of constant electromotive force in said path, said elements being supplied with current in multiple through said path, auxiliary electrodes for varying said currents n response to an impressed voltage, a receiving circuit and means for communicaing variations in said currents to said receiving circuit.

5. A receiving system comprising two electron discharge devices, each of said devices including an impedance controlling element, individual input circuits and individual output circuits for said devices, a portion of the similar circuits of said devices belng in common, and a high-impedance in the said common portion. I 6. In a receiving system for radio signaling, a power limiting device comprising separated elements, an impedance controlling means for controlling the impedance of the space between said elements, said device having input and output circuits, a source of current for said output circuit, and regulating means in the output circuit for causing the current supplied by said source to ap proach a maximum value as the input voltage is increased.

7. In a receiving system for radio signaling, a power limiting device comprising separated electrodes, an impedance controlling means for controlling the impedance between said electrodes, said device having input and output circuits, a source of power for said output circuit, and means responsive to the current in said output circuit for controlling the potential applied from said source across said electrodes whereby the rise of currents in said output circuit is limited.

8. In a receiving system for radio signaling, a power limiting device comprising an electron discharge element, an input circuit and an ouput circuit for said element, said output circuit having a portion which is traversed by fluctuating current passed by said element, and a high resistance in said portion.

9. In a receiving system for radio sig naling, a power limiting device comprising an electron discharge clement, an input circuitand an output circuit having a portion which is traversed by fluctuating current passed by said element, a source of cur rent for said output circuit, and a high resistance in said portion serially connected with said source for limiting the rise of current in said output circuit.

10. 1 receiving system for radio communication comprising an antenna, a receiving circuit connected therewith, means for detecting the waves communicated to said circuit, translating means responsive to said detected waves, and a device for limiting the power transmitted by said waves to said translating means; said device comprising an electron discharge device, a source of current therefor, and means for determining the intensity of the efi'ect produced in said translating means by a signal wave of a certain intensity and for preventing waves of greater intensity from exceeding said effect.

11. In a power limiting device, the 00111- bination of electron discharge devices each including an impedance varying element connected in opposition in a circuit, said elements having input and output circuitS, means for supplying current to said output circuits, means for preventing fluctuating currents from passing through said supplying means, and means for regulating the maximum value of the current furnished by said supplying means.

12. In a combination with a source of power, a-power limiting device comprising electron discharge repeaters with divided input and divided output circuits, a connection of said input circuit to said source of power, a path connected between the points of division of said circuits; said path comprising a source of electromotive force, means for preventing fluctuating currents from passing through said source, and means for regulating the maximum value of the current supplied from said source; a receiving device, and transformer windings for connecting'said output circuit to said receiving device.

13. In combination With 'a source of power, a power limiting device comprising electron discharge repeaters with divided input and divided output circuits, a connection of said input circuit to said source of power, a path connected between the points of division. of said circuits; said path comprising a source of electromotive force, an lmpedance device for preventing fluctuating currents from passing through said source, and a resistance for regulating the maximum value of the current supplied from said source; a receiving device, and trans former windings for connecting said output circuit to said receiving device.

14-. The combination of a receiving system comprising two electron discharge devices each including an impedance varying element, each having an input circuit and an output circuit, a portion of said output circuits being in common, and a. high impedance in the common portion of said output circuits.

15. In combination, a plurality of electronic discharge devices, each of said devices having an impedance varying element for influencing the space current flow therethrough in accordance with waves impressed thereon, a source of space currents for said devices, and means tending to maintain the sum of the space currents through said devices constant.

16. In combination, a plurality of electrical circuits each of said circuits including a conductive space, means including impedance varying elements for causing the impedance of said spaces to vary differently at different instants, a current supply source for said circuits, and means associated therewith tending to keep the sum of the currents through said circuits constant.

17. An amplifier comprising two electrical discharge devices, input and output circuits therefor, said devices being syinmetrically and oppositely disposed with respect to each of said circuits, space current paths for said devices, said paths having a common external portion of high impedance.

18. An amplifier comprising two electrical discharge devices, input and output circuits therefor, said devices being symmetrically and oppositely arranged with respect to each of said circuits, space current paths for said devices, a source of space current therefor, said paths having a common external portion, and means associated with said source for preventing fluctuating currents therethrough.

19. An amplifier comprising two space discharge devices, input and output circuits therefor, said devices being symmetricall and oppositely arranged with respect to eacli of said circuits, space current paths for said devices, said paths having a common external portion and a resistance in said portion which is large as compared with the normal impedance of the conductive space of one of said devices.

20. repeater comprising two electric discharge devices each having a cathode, an anode and an impedance varying element, a connection between said impedance varying elements, a connection between said cathodes, a connection between said anodes, an electrical impedance in one of said connections an electrical impedance in another of said connections, other connections from in termediate portions of each of said impedances to one of said first mentioned connections, one of said last named connections being provided with a source of current, and means tending to maintain a constant supply from said source.

21. In a repeater, two oppositely disposed electric discharge devices. lmpedance varying elements for said devices, means for causing one of said elements to increase the impedance of one of said devices, and the other of said elements to decrease the impedance of the other of said devices simultaneously, and means to cause the changes of current through said devices to be simultaneously substantially equal and opposite respectively when said repeater is repeating alternating current.

#2 In a signaling system, a power limiting device comprising an electron discharge device having an input circuit and an output circuit, a source of variable current connected to said input circuit, a path in said output circuit through which amplified variations from said source are constrained to pass, and a resistance located in said path of such a value that Waves of a normal value from said source will produce desired variations of current through said path, but impulses of a greater voltage will produce current having a maximum value not materially greater than the maximum value of current produced by waves of normal volt age applied to said input circuit.

23. In a signaling system, a power limiting device comprising an electron discharge device having input and output circuits, a source of space current for said output circuit, a path in said output circuit through which alternating current components are constrained to flow and a resistance in said path, said source and said resistance being of such values that incoming signal Waves will produce desired changes of current, but incoming waves of greater strength will produce only negligibly larger changes of current through said path.

24. A system for repeating alternating current comprising a plurality of electron discharge devices, an impedance varying element for one of said devices, a source of space currents for said devices, means tending to maintain the sum of the space currents through said devices constant, and means for utilizing the repeated alternating current.

25. A system for amplifying alternating or fluctuating current energy comprising two electrical discharge devices, input and output circuits therefor, said devices being symmetrically and oppositely disposed with respect to each of said circuits, and space current paths for said devices, said paths having a common portion external to said devices and of high impedance to currents of the frequencies to be amplified.

26. A receiving system comprising an electron discharge element, an input circuit and an output circuit for said element, said output circuit having a portion through which the fluctuating component of the current in said outputcircuit passes, said portion being of relatively high impedance to the fluctuating component.

27.- An amplifier comprising two electron discharge devices, an electron emitting cathode and an anode for said devices, space current circuits for said devices, said circuits having a common portion and individual portions, and a high impedance in said common portion.

' 28. In combination, a source of current, a plurality of electron discharge devices having space current paths, said paths being similarly connected to said source, one of said devices having an impedance varying element, and means tending to maintaln the sum of the space currents through said devices constant.

29. The method of overcoming the efiects of static disturbances in a wireless signaling system which consists in producing at a receiving station by means of the signaling current: an alternating current having a frequency much lower than the transmitted radio frequency current, and passing this current through a circuit containing a device for limiting the energy passing therethrough to a predetermined value.

30. The method of overcoming the effects of static disturbances in a wireless telephone receiving system which consists in first detecting the received signaling waves, thereby producing a varying current having a frequency much lower than the received waves, passing this current through a circuit containing a device for limiting the energy passing therethrough to a predetermined value and reproducing the telephone signal by the current passed through said circuit.

31. The method of reducing detrimental elfects of disturbing waves superimposed on waves to be received at a receiving station which comprises utilizing the energy of the received waves to produce a current which varies in amplitude at a frequency widely different from that of the received waves, and passing this current through a circuit containing a device for limiting the energy passing therethrough to a predetermined value. e

' 32. A system for reducing the detrimental effects of disturbing waves superimposed on waves to be received which comprises devices for producing at a receiving station by means of the received waves an alternating current of a widely different frequency from thatof the received waves, a circuit through which the alternating current is to "be'passed, and meansrfor limiting to a predetermined value the energy passing through said circuit. a

33. In an electric system, an incoming circuit and a pluralastage. amplifier for am plifying signals from said circuit comprising in one stage of said amplifier two vacuum tube repeaters connected in pushpull relation, and at least-one stage consist.- ing of a single vacuum tube amplifier feeding into said push-pull stage.

34. In an amplify'ng system in which the amplitude of the current increases in succeeding stages, a current responsive device actuated by the energy from said system, at

amplitude at which least one preliminary amplifying stage con stage consisting of a single vacuum tube re-- peater operating over a relatively small current amplitude range and giving amplification with the required degree of faithfulness of repetition of the signal and a stage into which said'single tube stage feeds, for amplifying the repeated-wave up to a current undesired distortion would take place in a single one of said tubes used alone, said later stage comprising a pair of vacuum tube repeaters connected in push-pull relation, whereby at said large current amplitude a faithfulness of repetition is obtained consistent with that of'thepreceding stage.

36. In combination, three electron discharge tubes, means for supplying discharge connected tu being so related to the current to said tubes, tvib of said tubes being connected in push-piill relation, the other .one of said t'ubesbemg arranged to'impress amplified si nalqvaves on said =push-pull so the peak amplitude of sai waves, for a given half-cycle the resultant momentary decrease .in the normal discharge current through one of said push-pull connected tubes reduces the discharge current through said tube near to zero.

37. In combination a pair of space discharge devices, each of said devices having a'cathode, an anode and a grid or control element, anode .circuits and grid circuits for said devices, a common source of discharge current connected to said anodes, a common source of alternating current potential connected to said grids, said devices being connected to operate in pushullrelation, the normal discharge current t rough said tubes amplitude of the al tcrnating potential impressed on said grids that at the peak amplitude of said alternating potential the space current through one and the other of said devices alternately is reduced substantially to zero.-

In an electric system, an incoming circuit and a plural stage amplifier for amplifying signals fromsaid circuit, said amplifier comprising at least one stage consisting of a single electron discharge tube and a stage consisting of a pair of electron dis charge tubes connected in push-pull relation, having their input sides connected'to the output side of said first mentioned stage, means for supplying discharge current to said tubes, the amplitude of the signal variations in the discharge current of said pushpull tubes being of the order of magnitude of the normal discharge current' through said tubes. 7 I

In witness whereof, I hereunto subscribe my name this 31st day of August A. D., 1915.

HAROLD DE FOREST ARNOLD.

such am litude that at a DISCLAIMER 1,504,537.Harold De Forest Arnold, Maplewood, N. J. POWER-LIMITING AMPLIFY- ING DEVICE. Patent dated August 12, 1924. Disclaimer filed June 24, 1933, by the assignee, American Telephone and Telegraph Company.

Hereby enters this disclaimer to claims 17, 18, 20, 33, 34, 35, and 36 of said Letters Patent, to wit:"

17. An amplifier comprising two electrical discharge devices, input and output circuits therefor, said devices being symmetrically and oppositely disposed with respect to each of said circuits, space current paths for said devices, said paths having a common external portion of high impedance.

18. An amplifier comprising two electrical discharge devices, input and output circuits therefor, said devices being symmetrically and oppositely arranged with re spect to each of said circuits, space current paths for said devices, a source of space current therefor, said paths having a common external portion, and means associated with said source for preventing fluctuatingcurrents therethrough.

20. A repeater comprising two electric discharge devices each having acathode an anode and an impedance varying element, a connection between said impedance varying elements, a connection between said cathodes, a connection between said anodes, an electrlcalnnpedance in one of said connections, an electrlcal impedance 1n another of said connections, other connect1onsfrom lntermediate portions of each of said impedances to one of said first mentioned connections, one of saidlast named a constant supply from said source. I I

33. In an electric system, an incoming circuit and a plural stage amplifier for amplifying signals from said circuit comprising in one stage of said amplifier two vacuum tube repeaters connected in push-pull relation, and at least one stage consisting of a single vacuum tube amplifier feeding into said push-pull stage.

34. In the amplifying system in which the amplitude of the current increases in succeeding stages, a current responsive device actuated by-the energy from said system, at least one preliminary amplifying stage consisting of a single vacuum connections being provided vwith a source of current, and means tending to maintain tube amplifier oircuit,' and a succeeding stage for delivering the amplified current, .to sald responsive device, sald last mentioned stage comprising a pair of vacuum tube amplifiers connected in push-pull relation.

35. In a plural stage amplifier circuit for amplifying signal currents, employing vacuum tube amplifiers in which, for relatively strong output currents at least, as the amplitude of the repeated wave becomes larger the distortion of the wave increases, said amplifier circuit comprising at least one stage consisting of a single vacuum tube repeater operating over a relatively small current amplitude range and giving amplification withthe re uired degree'of faithfulness of repetition of the signal and a stage into which sai single tube stage feeds, for amplifying the repeated wave up to a current amplitude at which undesired distortion would take place in a single one of said tubes used alone, said later stage comprising a pair of vacuum tube repeaters connected in push-pull relation, whereby at said large current amplitude a faithfulness of repetition isobtained consistent with that of the preceding stage.

36. In combination, three electron discharge tubes, means for supplying discharge current to said tubes, two of said tubes being connected in push-pull relation, the other one of said tubes being arranged to impress amplified signal waves on said push-pull connected tubes of such amplitude that at the peak amplitude of said waves, for a given half-cycle the resultant momentary decrease in the normal discharge current through one of saidpush-pull connected tubes reduces the discharge current through said tube near to zero.

[017ml Gazette July 18,1933.] 

